This invention relates to an inductor device, and more particularly, to a transformer having connections whereby changes in coil length are readily achievable.
Large manufacturing firms with markets all over the world are finding it necessary to provide equipment that is capable of operating from a variety of power sources of different voltages and frequencies. Equipment with a relatively high kilovolt-amp (KVA) rating such as large computers are commonly connected to three-phase power lines. In the United States the common three-phase power source is 208 volts, line-line at sixty hertz. In England and most of the United Kingdom the common three-phase power source is 415 volts, line-line at fifty hertz. Continental Europe supplies power at fifty hertz and at 220 volts line-line or at 380 volts, line-line, depending on the particular location. In Japan the common voltage is 200 volts line-line. The frequency in Japan is fifty hertz in some locations and sixty hertz in others.
Because the destination of a particular piece of equipment is not generally known at the time of its manufacture, and also because equipment standardization tends to yield lower manufacturing costs, it is desirable that a single equipment design should be able to accommodate as many of the various world voltages and frequencies as possible, and that any adjustments or special connections that are required at a specific site should be kept to a minimum and also kept as simple as possible. Hardware elements incorporated in equipment to permit utilizing the local power sources should also be as simple and inexpensive as possible.
The problem (i.e., providing connectability to a variety of voltage and frequency combinations) is exacerbated when ferro-resonant transformers are incorporated in the equipment for pre-regulation and buffering against voltage dips and surges. In such cases, it is necessary to provide separate taps for each frequency even if the voltages are the same. When both frequency and voltage are taken into consideration, it is not unusual to find that at least three taps are required at each transformer primary. In the present invention, there is provided a mechanism for selecting the appropriate tap for a given input voltage and frequency.